The invention relates to a cutting device for cutting or bursting pipelines.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
A cutting device is disclosed for example in German Pat. No. DE 198 31 190 C1. The cutting device is pulled via a linkage through a pipeline to be cut and provided on one side of an elongate basic body with three rotatably mounted cutting rollers arranged in a line and at a distance from one another. Situated opposite each of the cutting rollers is a support roller which is used to bear the transverse forces on the pipe shell caused by the cutting rollers.
The first cutting roller as seen in the pulling direction is offset from the central position to such an extent that its cutting edge directly severs the pipe shell across its full thickness.
The two following cutting rollers are arranged with an even greater offset in the direction of the pipe shell than the first cutting roller. They are responsible for reliably severing periodically occurring pipe sleeves or isolated repair clamps.
High pulling forces are required in the case of such cutting rollers which cut the pipe continuously in the longitudinal direction. These pulling forces must be borne by the old underground pipe to be cut and at the front plate of the pulling device used. Where there is major damage to the old pipe, as may be caused for example by pitting, the force can no longer be reliably transmitted via the old pipe and the old pipe may be caused to buckle. In this case, whole pieces of pipe may break off depending on the pipe material, or the pipe pushes in on itself to form corrugations. This may considerably hinder the subsequent cutting operation or make it impossible.
Furthermore, the pipe fragments broken off may result in damage to a new pipe which is subsequently pulled in.
It would therefore be desirable and advantageous to provide an improved cutting device and improved method for cutting pipelines in the longitudinal direction to obviate prior art shortcomings.